Lactogenic Hormone Prolongs the Time During Which Deciduomata May be Induced in Lactating Rats. ∗

The ability to produce deciduomata is an indicator of corpus luteum activity. This functional test has been used as evidence that the corpora were active during lactation in the rat. Inasmuch as deciduomata can be produced as late as the sixteenth day of lactation, 1 the corpora function normally for approximately this duration. Although the corpora do not function for any appreciable period after this time, it has been possible by progesterone administration to prolong the period during which deciduomata may be produced. 2

Recently 3 purified lactogenic hormone has been given hypophysectomized rats to produce deciduomata. This appears to demonstrate a gonadotropic function of this hormone. In these experiments the corpora lutea appeared large and healthy even when the follicles, as well as the interstitial tissue were below normal. Furthermore in this same work the effectiveness of lactogenic hormone in producing the growths in adrenalectomized rats was demonstrated.

Fifteen lactating rats were subjected to uterine stimulation as late as the twenty-fourth postpartum day and were thereafter injected subcutaneously with 100 I.U. of commercial lactogenic hormone† daily for 4 days. As shown in the table, 13 of the 15 animals, sacrificed on the 5th day, showed microscopically confirmed deciduomata, together with large robust-appearing corpora lutea. Eight uninjected control animals showed small regressive corpora and no deciduomata at the sites previously stimulated. The results are interpreted as further evidence of corpus luteum stimulation by the lactogenic hormone.

Presumably this gonadotropic function is mediated by the continued production of progestin in the corpora in sufficient concentration to permit the growth of the deciduomata well past the time when they can normally be produced.